Q2. Calculate the number of fatigue cycles required to increase the crack length from 1mm to 20mm for a semicircular surface flaw on a metallic structure. The fatigue coefficient of the material for the Paris equation is A=6.871012mcycle1(MPam)3 and the stress range is 60MPa. Assume that the crack length is small compared to the cross-section of the structure, such that KI=1.12a. Also calculate the percentage change in the number of cycles if the initial crack size is twice as long. [10]